Workload assumptions for structural radiation protection calculations

The UK Health Protection Agency guidance "Recommendations for the design of X-ray facilities and the quality assurance of dental cone beam CT (Computed Tomography) Systems" published February 2010 recommends assuming 20 scans per week for a CBCT installed in dental practice and 50 scans per week for a unit installed in a hospital department. This was based on the experience of members of an HPA working party and was thought to be maximum likely in these 2 scenarios.

Are these reasonable figures to recommend, given that any structural protection should be designed to be adequate for the likely lifetime of the CBCT unit? If not, what would you suggest?

I believe 50 per week for a hospital (or private radiology practice) is a reasonable maximum, at Leuven the device which is used the most could have 10 patients/day in extreme cases, but averages on about 25-30 patients/week which may peak to about 40.

For dental practices, I think 20 may be on the low side, judging from the experience I have visiting private practices to perform tests on their CBCTs. On some occasions, we had to stop scanning numerous times to allow for a patient to be scanned. So for large implantology practices, there could well be about 30 patients/week, similar to hospital workloads.

We could of course contact all known CBCT owners in Belgium, UK, etc. to ask for estimates on patient workload. I'm sure we will get useful figures from that which can help to define general workloads.